Harvest, I think, is our best option. I love Tropius with THE FIRE OF A THOUSAND SUN TEAMS, but the real reason is for it's Versatility
Giving a poké more the one role can never be necessarily bad. Salac berry vs. Sitrus give you two completely different play styles. Being able to move in more then one direction will be helpful in countering a variety of threats from different sides of the rain.
Do I want to survive scizor or deal with l@tios?
Is politoed a larger threat for my team then Ferrothorn?
Choosing in this situation means that you give the player more options - and more limits - depending on what berry and therefore what set they choose.
In a sense, it lets CAP 5 be a jack of all trades without being a true jack of all trades.
Chlorophyll on the other hand is just a cheap stat boosting option. I mean, hell, Harvest can do that too, so why not have it instead? Chloro limits our uses and limits the value of something that could be so versatile. Why limit your options to "outspeeding latios" when you could instead change that to "outspeeding latios" or "beating politoed" or "being everything Tropius could've been without being complete and utter shizzle, my fizzle," and none of them being on the same set? It's like making 3 or 4 different Pokemon at the same time.
Look at Breloom, for example. Technician Breloom plays completely different from Poison Heal Breloom. Now imagine if instead of it being two different abilities, it was two different items? HARVEST IS FLIPPING MAGIC! Do it for Tropius!
A choice banded critical V-create from darmantian with a +6 boost to attack, sunshine, and an adamant nature on a level 1, dry skin, mild paras with a -6 boost to defence and 0 IVs in defence will do 16648780 - 19586808 Damage.